Diffusion weighted imaging and B-cell lymphoma/leukemia-2 gene-related research in rabbit models of hepatic VX2 tumors after radiotherapy

Abstract

Objective To study the DWI characteristics,Bcl-2 gene expression and the relevance of the DWI and Bcl-2 in rabbit models of hepatic VX2 tumors after three-dimensional conformal radiation therapy(3D-CRT).Methods Forty hepatic VX2 tumor models were successfully created.After the tumor grew to more than 1 cm in diameter,28 tumor models were treated with 3D-CRT and then divided into four groups using random number table.The remaining 12 tumor models were used as controls and randomly assigned to each group.MR scanning were performed at different times(1st day,5th day,10 th day,15 th day) for each group respectively.ROIs of the VX2 tumor tissue and normal liver tissue were taken and ADC values measured with calculation of their ratio.Expression of apoptotic Bcl-2 gene was determined by using Rt-PCR method.ADC value with their ratio and the relative gray value of Bcl-2/β-actin were calculated using one dimensional analysis of variance and two samples t-test at different times,compared within the group and between groups.Results On the 1st,5 th,10 th and 15 th day,the ADC ratios of the radiotherapy groups were 0.55±0.13,1.32±0.27,0.96±0.34,0.72±0.17 respectively,the corresponding ADC ratios of control groups were 0.69±0.20,0.78±0.24,0.71±0.23,0.79±0.21.The ratio of ADC values for radiotherapy group and the control group were compared,t value was 1.283(P＞0.05),4.974(P＜0.01),3.191(P＜0.01),0.776(P＞0.05)respectively for each group.On the 1st,5 th,10 th and 15 th day,the Bcl-2 gene relative gray value of the radiotherapy groups were 0.92±0.31,0.56±0.28,0.42±0.24 and 0.31±0.15 respectively,the corresponding Bcl-2 gene relative gray value of control group were 1.18±0.50,1.15±0.43,1.16±0.41,1.46±0.19.The Bcl-2 gene relative gray value for radiotherapy groups and the control groups were compared,with t value 0.987(P＞0.05),3.863(P＜0.01),5.401(P＜0.01),5.894(P＜0.01)respectively.The ADC value ratio and Bcl-2 gene relative gray value correlation analysis showed that there was significant negative correlation(r=-0.493,P＜0.01).Conclusion DWI ADC values can reflect the dynamic changes at the molecular level for hepatic VX2 tumors after radiotherapy at different times. Key words: Carcinoma,hepatocellular; Diffusion magnetic resonance imaging; Model,animals; Genes,bcl-2